Sheet-material forming device and method

ABSTRACT

The present invention relates to a sheet-material forming device and method which can be easily changed in response to modifications and changes in a target shape and which can implement forming even curved surfaces with edges or localized small radiuses of curvature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/KR2010/009383, filed Dec. 28, 2010, and published in Korean as WO/2011/081387 on Jul. 7, 2011. This application claims the benefit and priority of Korean Application No. 10-2009-0132250, filed Dec. 28, 2009. The entire disclosures of the above applications are incorporated herein by reference.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

TECHNICAL FIELD

The present invention relates to an apparatus and method for fabricating sheet-material products, such as external plates for ship, railway vehicles, aircraft, and vehicles and, more particularly, to a sheet-material forming apparatus and method for forming a sheet type product having surfaces with multiple curvatures, local curvatures and/or edges.

Discussion

In general, in forming a sheet type product having curved surfaces with multiple curvatures, local curvatures and/or edges, a forming apparatus and method using a mold is widely being used. The sheet-material forming apparatus and method using a mold are being widely used in processing for, in particular, sheet materials for external structures of vehicles.

A conventional sheet-material forming apparatus and method includes upper and lower molds corresponding to a target shape and implement forming of a sheet type product with the molds coupled with a press.

The sheet-material forming apparatus and method are effective in the mass production of single shape products since the upper and lower molds are shaped corresponding to the product, however, it is not suitable for small quantity batch production since new entire molds must be fabricated when a target shape is modified which increase the cost and time.

In particular, in case of a sheet type product for an external structure of a vehicle, a target shape is modified several times during the design step, so the conventional sheet-material forming apparatus and method is not suitable in this case in terms of expenses and the time because the molds must be newly fabricated whenever the shape and structure of the external structure are changed.

In order to solve this problem, U.S. Pat. No. 4,212,188 and Japanese Patent Laid-Open Publication S46-37088 disclose a multi-point variable press type sheet-material forming apparatus in which upper and lower molds include a plurality of punches individually moved up and down. The multi-point variable press type sheet-material forming apparatus is advantageous since the shape of the molds can be changed by adjusting the heights of punches when a target shape is modified.

However, the known multi-point variable press type sheet-material forming apparatus is effective in forming gently curved surface, but has difficulties in forming surface with edges or locally small radius of curvature. Therefore, the conventional sheet-material forming apparatuses are limited in use and cannot flexibly response to the modifications of a target shape.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a sheet-material forming apparatus and method which are flexible in handling the modifications and changes of a target shape and which are advantageous for small quantity batch production or for the sheet-material forming for an external structure of a vehicle during its designing process.

Another object of the present invention is to provide a sheet-material forming apparatus and method which are capable of forming a curved surface having a locally small radius of curvature and/or edges easily.

To achieve the above objects, a sheet-material forming apparatus according to the present invention includes upper and lower variable molds configured to be movable up and down between which a sheet material to be formed interposed, the upper and lower variable molds being constructed by combining a plurality of mold blocks for forming curved surface with different radiuses of curvature and locally small radiuses of curvature and/or edges. The plurality of mold blocks comprises at least one forming punch block having an array of punches for forming curved surface with various radiuses of curvature and at least one integral forming block having a part for forming curved surface with locally small radiuses of curvature and/or edges.

In accordance with a preferred embodiment, the forming punch blocks may comprise first, second, third, . . . , N^(th) forming punch blocks, in each of which the punches having cross-section of different sizes are arranged, and each of the forming punch blocks may include a support member for supporting the corresponding punches and for being combined with a neighboring mold block.

Further, each of the punches of the forming punch blocks may be constructed to be adjustable in its height, and each of the punches may have a circular or a polygon cross-section and a rounded end.

Furthermore, elastic pads for forming smooth curved surface may be interposed between the forming punches of the upper and lower variable molds and the sheet material to be formed.

In accordance with a preferred embodiment, the integral forming block may comprise at least one edge block for forming curved surface with an edge and/or at least one small-radius-of-curvature block for forming curved surface with a small local radius of curvature, and each of the edge blocks and the small-radius-of-curvature blocks may comprise a support member for supporting the forming part and for being combined with a neighboring mold block.

Furthermore, the sheet-material forming apparatus according to the present invention may further comprise a fixing die for the plurality of mold blocks combined based on a target shape of the sheet material to be formed and a punch height adjustment module for adjusting heights of the punches to produce a forming surface corresponding to the target shape.

Meanwhile, a sheet-material forming method according to the present invention includes the steps of modeling a target shape; selecting mold blocks corresponding to the shape and the curvature of surface resulting from the modeling of the previous step, combining the selected mold blocks, and adjusting heights of punches, in order to construct a forming surface corresponding to the target shape; correcting the constructed forming surface; and finally forming the sheet material.

The step of correcting the constructed forming surface may be a method based on a test, including the steps of forming a trial product; measuring error of the shape of the trial product and determining whether the measured error falls within a tolerance; and reconstructing a corrected forming surface, if the measured error of the trial product is not within the tolerance.

Alternatively, the step of correcting the constructed forming surface may be a method based on analysis, including the steps of analyzing the constructed forming surface; evaluating an amount of elastic recovery of the sheet material through elastic recovery analysis; predicting the shape of a trial product based on the evaluation and determining whether the error of the trial product falls within a tolerance; and reconstructing a corrected forming surface, if the error of the trial product is not within the tolerance.

In the sheet-material forming method according to the present invention, the step of reconstructing a corrected forming surface may be repeatedly performed until the trial product satisfies the tolerance, regardless which correction method is used.

In accordance with the present invention, according to the modifications of a target shape, upper and lower molds for forming can be easily changed, since variable molds are constructed by selecting and combining forming punch blocks and integral forming blocks (edge blocks or small-radius-of-curvature blocks) corresponding to a target shape. In particular, a surface with edges or a localized small radius of curvature which was difficult to be formed with a conventional forming punch block can be easily formed through a combination of prefabricated integral forming blocks with forming punch blocks.

Accordingly, in a small quantity batch production, cost reduction and productivity improvement can be achieved because new and different entire molds are not required to be fabricated for each type. Furthermore, in the designing process of, for example, a vehicle, in which the modifications of the target shape are frequently necessary, the cost and time can be reduced, because new entire molds are not required to be fabricated whenever the external shape is modified.

Furthermore, the sheet-material forming apparatus and method according to the present invention can be used regardless of the type and thickness of materials. Therefore, the apparatus and method can be advantageously used for forming a curved surface having a single curvature, dual curvatures, multiple curvatures, and localized small radiuses of curvature or edges in the different materials or different thicknesses, isotropy or anisotropy materials in terms of the cost and time.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIGS. 1 and 2 are perspective views showing examples of a forming punch block which constitutes a variable mold of a sheet-material forming apparatus according to the present invention,

FIG. 3 is a perspective view of an edge block which is an example of an integral forming block which constitutes a variable mold of the sheet-material forming apparatus according to the present invention,

FIG. 4 is a perspective view of the small-radius-of-curvature block of an integral mold block which constitutes a variable mold of the sheet-material forming apparatus according to the present invention,

FIG. 5 is a sectional view showing an example of a variable mold constructed by combining the various mold blocks,

FIG. 6 is a sectional view showing the sheet-material forming apparatus in which a sheet material is formed by using the variable mold of FIG. 5,

FIG. 7 is a sectional view showing another example of a variable mold constructed by combining the various mold blocks,

FIG. 8 is a sectional view showing the sheet-material forming apparatus in which a sheet material is formed by using the variable mold of FIG. 7,

FIG. 9 is a perspective view showing an example of 3-D modeling of a target shape,

FIGS. 10A and 10B are plan and sectional views of the variable mold constructed to correspond to the target shape of FIG. 9,

FIG. 11 is an exploded perspective view showing an example of an installation including a variable mold, a fixing die, and a punch height adjustment module,

FIG. 12 shows the assembled installation of FIG. 11, and

FIG. 13 is a process diagram of a sheet-material forming method using the sheet-material forming apparatus according to the present invention.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example embodiments will now be described more fully with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. For reference, in describing the embodiments of the present invention, a detailed description of the known functions and constructions will be omitted if it is deemed to make the gist of the present invention unnecessarily vague.

FIGS. 1 to 4 illustrate mold blocks which can be combined for a variable mold of a sheet-material forming apparatus according to an embodiment of the present invention, FIGS. 1 and 2 schematically show embodiments of forming punch blocks, and FIGS. 3 and 4 schematically show embodiments of integral forming blocks.

As shown in FIGS. 1 and 2, forming punch blocks 10 and 20 include respectively a plurality of punches 11 and 21 arranged in rows and columns, and respectively support members 12 and 22 that support the punches 11 and 21.

The respective punches 11 and 21 have different diameters. The forming punch block 20 including the punches 21 each having a relatively large diameter is for forming a relatively gentle curved surface part, and the forming punch block 10 including the punches 11 each having a relatively small diameter is for forming a relatively sharp curved surface

Meanwhile, although not shown, the sheet-material forming apparatus according to the present invention comprises a plurality of forming punch blocks 10, 20, . . . , N including punches having various diameters. Curved surfaces having various radiuses of curvature, therefore, can be formed by using the plurality of forming punch blocks 10, 20, . . . , N.

Further, although FIGS. 1 and 2 illustrate that the punches 11 and 21 have a circular cross-section, the punches 11 and 21 may also have a polygon cross-section, such as a triangle or a square. Furthermore, the punches 11 and 21 may preferably have rounded ends as shown in FIGS. 5 to 8.

The support members 12 and 22 support the respective punches 11 and 21. The height of each of the punches 11 and 21 can be adjusted in the state that the punches 11 and 21 are supported by the support members 12 and 22. The respective adjustment of the height of the punches 11 and 21 is implemented by a punch height adjustment module 400 shown in FIGS. 11 and 12. Further, each of the support members 12 and 22 is equipped with a fastening structure, not shown in detail, for combination with a neighboring mold block. The fastening structure is a conventional detachable fastening structure, and a detailed description thereof is omitted.

As shown in FIGS. 3 and 4, integral forming blocks 30 and 40 are equipped with respective forming parts 31 and 41 and respective support members 32 and 42 that support the parts 31 and 41.

The part 31 of the integral forming block 30 shown in FIG. 3 is for forming an edge, and the part 41 of the integral forming block 40 shown in FIG. 4 is for forming curved surface having a locally small radius of curvature. Further, each of the support members 32 and 42 has a fastening structure, not shown, for coupling the blocks with a neighboring mold block. The fastening structure is a conventional detachable fastening structure, and a detailed description thereof is omitted.

FIGS. 3 and 4 each shows the edge forming part 31 or the small-radius-of-curvature forming part 41 with an example shape, but the sheet-material forming apparatus according to the present invention may include a plurality of integral forming blocks 30, 40, . . . , N having respective forming parts with various shapes.

As mentioned above, Upper and lower variable molds having a forming surface corresponding to a specific target shape can be constructed by properly selecting and combining the plurality of mold blocks shown in FIGS. 1 to 4. For example, when a kind is changed in a small quantity batch production process or an external shape is modified during a vehicle design, a variable mold can be immediately reconfigured to make a desired forming surface by selecting corresponding ones from the prefabricated forming punch blocks 10, 20, . . . , N and integral forming blocks 30, 40, . . . , N. Therefore, it is not necessary to fabricate a new entire mold, and the cost and time for producing a new entire mold can be saved.

Meanwhile, although all the edge blocks or the small-radius-of-curvature blocks corresponding to all possible shape cannot be previously fabricated, a variable mold can be constructed by producing only an integral forming block corresponding to a changed part and by combining it with the existing mold blocks. Accordingly, even in these cases, the cost and time can be much reduced as compared with fabricating a new entire mold

FIGS. 5 to 8 show examples in which a variable mold having a forming surface corresponding to a target shape is constructed by combining the above-described mold blocks. FIGS. 5 and 6 show an example of variable molds when a desired forming surface has edges, and FIGS. 7 and 8 show an example of variable molds when a desired forming surface has small localized radiuses of curvature.

In the example shown in FIG. 5, a lower variable mold 100 has in the center the forming punch block 20 in which the punches 21 each having a relatively large diameter are arranged in order to form gently curved surface, and on both sides of the forming punch block 20 two edge blocks 30 and 30′ having respective parts 31 and 31′ for forming curved surface with edges, and on both ends forming punch blocks 10 and 10′ in each of which the punches 11 each having a relatively small diameter in order to form sharp curved surface.

The mold blocks 10, 30, 20, 30′, and 10′ disposed as described above are combined with each other through the respective support members 12, 32, 22, 32′, and 12′. The punches 11, 21, and 11′ of the forming punch blocks 10, 20, and 10′ are adjusted in its heights based on the curvature of a target shape. Further, the punches 11, 21, and 11′ have elastic pads 50 on top for forming smooth curved surfaces.

FIG. 6 also show an upper variable mold 200 and a sheet material P to be molded. The upper variable mold 200 is constructed just as the lower variable mold 100, but the forming surface profile of the upper variable mold 200 is opposite to that of the lower variable mold 100 so that the sheet material can be formed to have one shape by using the upper and lower variable molds 200 and 100.

The upper and lower variable molds 200 and 100 constructed as described above are connected with, for example, a press, not shown, and the sheet material P is placed between the upper and lower variable molds 200 and 100. By actuating the press, the upper and lower variable molds 200 and 100 are brought to close to each other and to implement forming the interposed sheet material P into a desired target shape. Here, elastic pads 50′ can be also interposed between the respective punches 11 a, 21 a, and 11′a of the upper variable mold 200 and the sheet material to be formed P in order to produce gently curved surface.

FIGS. 7 and 8 show an example of reconstructed variable molds when the target shape of a sheet material is partially changed, that is, the target shape has curved surface with localized small radiuses of curvature instead of edges in FIGS. 5 and 6.

In this case, new upper and lower variable molds 200′ and 100′ are constructed by replacing the edge blocks 30 and 30′ with the respective small-radius-of-curvature blocks 40 and 40′. The remaining elements other than the small-radius-of-curvature blocks 40 and 40′ are the same as those described above with reference to FIGS. 5 and 6 and are assigned the same or similar reference numerals as those of FIGS. 5 and 6, and thus a detailed description thereof is omitted.

As described above, when a target shape is modified, product forming is enabled rapidly with low cost in such a manner that a variable mold is reconfigured to make a new forming surface corresponding to the changed target shape by replacing only a forming block corresponding to the changed part. Further, even in the case when there is no previously fabricated forming block corresponding to the changed part, a variable mold can be reconstructed by only fabricating a new forming block corresponding to the changed part and combining the block with existing other mold blocks. Accordingly, the cost and time can be significantly reduced as compared with the case where the entire mold is newly fabricated.

Meanwhile, if the curvature of surface of a target shape is changed, a forming surface corresponding to the target shape can be constructed easily and rapidly by simply adjusting the heights of the punches of forming punch blocks.

FIG. 9 is a perspective view showing an example of 3-D modeling of a target shape. In accordance with this example, the target shape includes a relatively gently curved surface part 5-1, relatively sharp curved surface parts 5-2 and 5-3, and surface parts with edges 5-4 and 5-5.

FIGS. 10A and 10B are plan and sectional views of a lower variable mold 100 constructed by combining mold blocks selected based on the 3-D modeling of the target shape and by adjusting the heights of punches based on the curvatures of surface of the target shape.

As shown in FIGS. 10A and 10B, the variable mold 100 includes a forming punch block 20 with punches each having a relatively large diameter in the position corresponding to the gently curved surface part 5-1, and forming punch blocks 10 and 10′ with punches each having a relatively small diameter in the position corresponding to the respective sharp curved surface parts 5-2 and 5-3, and edge blocks 30 and 30′ in the position corresponding to the edge surface parts 5-4 and 5-5. Here, the punches are adjusted in its heights based on the curvature of the surface parts. Further, the punches can have elastic pads 50 on top.

FIG. 11 is an exploded perspective view of an example an installation of a variable mold for forming a shape including surfaces both edges and localized small radiuses of curvature, a fixing die for the variable mold, and a punch height adjustment module. FIG. 12 shows the assembled installation of FIG. 11.

As shown in FIGS. 11 and 12, the variable mold 100 is constructed by coupling forming punch blocks 10 and 10′ with punches 11 and 11′, an edge block 30, and a small-radius-of-curvature block 40.

The variable mold 100 constructed as described above is inserted into or coupled to the fixing die 300. The fixing die 300 not only fastens the variable mold 100 having the plurality of mold blocks but also support an upper variable mold (not shown).

The punch height adjustment module 400 is disposed under the fixing die 300. The punch height adjustment module 400 may include adjustment motors equal to the number of punches to change the heights of punches by moving the punches up and down individually. Alternatively, the punch height adjustment module 400 may be configured in such a manner that one to four adjustment motors move in row and column directions to adjust the heights of the punches.

In accordance with a preferred embodiment, the punch height adjustment module 400 receives data of the curved surface of a target shape and adjusts the punches to be forming the curved surface by controlling the adjustment motors.

A method of forming a sheet material by using the sheet-material forming apparatus explained above is described below with reference to FIG. 13.

Firstly, a target shape is subject to 3-D modeling (S510). Then, mold blocks corresponding to the shape and the curvature of surface resulting from the modeling are selected, the selected mold blocks are combined, and heights of punches are adjusted, in order to construct a forming surface corresponding to the target shape (S520). Then, a correction process is performed on the forming surface primarily constructed (S530)

The correction process (S530) can be performed by using a method based on a test or a method based on analysis (S531). In the correction method based on a test, first, a trial product is produced by using variable molds primarily constructed as described above (S532). Then, an error is measured for the shape of trial product obtained by the forming at the previous step (S533), and it is determined whether the measured error falls within an a tolerance (S534).

If it is determined that the measured error of the shape of trial product satisfies the tolerance, forming a sheet material is implemented (S540). If, however, it is determined that the measured error is not within the tolerance, a step of reconfiguring the forming surface is performed (S535).

Here, in the step of reconfiguring the forming surface, the punches are again adjusted in its heights and the integral forming blocks are replaced to compensate the measured error.

After then, a trial product is produced again by using the corrected variable molds, an error is measured for the shape of the new trial product, and it is determined whether the measured error falls within the tolerance. If the measured error satisfies the tolerance, forming a sheet material is implemented. Otherwise, the step of reconfiguring the forming surface is repeated.

In the correction method based on analysis, first, forming analysis into the primarily constructed forming surface is performed by using a computer (S536). Then, elastic recovery analysis into a sheet material is performed by a limited element method (S537), and by which the shape of a trial product is predicted (S538). If the shape satisfies a tolerance, forming a sheet material is implemented (S540). However, if the shape does not satisfy the tolerance, the step of reconfiguring the forming surface is performed (S535).

After a forming surface is reconfigured as described above, the shape of a trial product is again predicted by performing forming analysis and elastic recovery analysis into the corrected forming surface. Again, if the shape satisfies the tolerance, forming a sheet material is implemented, and if not, reconfiguring the forming surface is performed (S535). These steps are repeated until the shape of the trial product satisfies the tolerance.

As described above, the sheet-material forming method according to the present invention can reduce errors by forming a sheet material after correcting the forming surface, and the forming surface constructed by combining a plurality of mold blocks can be easily corrected by changing the mold blocks.

The present invention has been described as exemplary manner. The terms used herein are only for a description and should not be interpreted as limited meanings. The present invention may be modified and changed in various ways. Accordingly, the present invention may be freely executed within the scope of the claims, unless otherwise described.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention. 

1-12. (canceled)
 13. A sheet-material forming apparatus comprising: upper and lower variable molds configured to be movable up and down with a sheet material to be formed interposed between the variable molds, wherein the upper and lower variable molds are constructed by combining a plurality of mold blocks, wherein the plurality of mold blocks includes: at least one forming punch block having an array of punches for forming curved surface with various radiuses of curvature; and at least one integral forming block having a part for forming curved surface with locally small radiuses of curvature and/or edges.
 14. The sheet-material forming apparatus according to claim 13, wherein: the forming punch block comprises first, second, third, . . . , N^(th) forming punch blocks, in each of which the punches having cross-section of different sizes are arranged, and each of the forming punch blocks includes a support member for supporting the corresponding punches and for being combined with a neighboring mold block.
 15. The sheet-material forming apparatus according to claim 13, wherein each of the punches of the forming punch block is adjustable in the height.
 16. The sheet-material forming apparatus according to claim 13, wherein each of the punches of the forming punch block has a circular cross-section and a rounded end.
 17. The sheet-material forming apparatus according to claim 13, wherein each of the punches of the forming punch block has a polygon cross-section and a rounded end.
 18. The sheet-material forming apparatus according to claim 13, wherein the forming punch block further comprise elastic pads interposed between the punches and the sheet material to be formed for forming smooth curved surface.
 19. The sheet-material forming apparatus according to claim 13, wherein: the integral forming block comprises at least one edge block for forming curved surface with an edge and/or at least one small-radius-of-curvature block for forming curved surface with a small local radius of curvature, and the edge block and the small-radius-of-curvature block comprise a respective support member for supporting the block and for being combined with a neighboring mold block.
 20. The sheet-material forming apparatus according to claim 13, further comprising: a fixing die for the plurality of mold blocks combined based on a target shape of the sheet material to be formed; and a punch height adjustment module for adjusting heights of the punches to produce a forming surface according to the target shape.
 21. A sheet-material forming method using the sheet-material forming apparatus according to claim 13, comprising the steps of: a) modeling a target shape; b) selecting mold blocks corresponding to the shape and the curvature of surface resulting from the modeling of the step a), combining the selected mold blocks, and adjusting heights of punches, in order to construct a forming surface corresponding to the target shape; c) correcting the constructed forming surface; and d) finally forming the sheet material.
 22. The sheet-material forming method according to claim 21, wherein the step c) comprises the steps of: forming a trial product; measuring error of the shape of trial product and determining whether the measured error falls within a tolerance; and reconstructing a corrected forming surface, if the measured error of the trial product is not within the tolerance, wherein the step of reconstructing a corrected forming surface is performed repeatedly until the trial product satisfies the tolerance.
 23. The sheet-material forming method according to claim 21, wherein the step c) comprises the steps of: analyzing the constructed forming surface; evaluating an amount of elastic recovery of the sheet material through elastic recovery analysis; predicting the shape of a trial product based on the evaluation and determining whether the error of the trial product falls within a tolerance; and reconstructing a corrected forming surface, if the error of the trial product is not within the tolerance, wherein the step of reconstructing a corrected forming surface is performed repeatedly until the trial product satisfies the tolerance. 